The invention relates to a low-pressure apparatus for carrying out steps in the manufacture of a device, in particular, but not exclusively, a semiconductor device, which steps are performed under a prescribed pressure, the apparatus comprising:
a reactor chamber for accommodating a body,
a gas supply pipe for introducing a process gas flow, which gas supply pipe is connected to the reactor chamber,
an exhaust pump for evacuation, which exhaust pump is connected to the reactor chamber through an exhaust pipe,
a pressure control valve for adjusting a valve opening, which pressure control valve is provided on the exhaust pipe,
a pressure sensor for monitoring the pressure inside the reactor chamber, and
control means for controlling the valve opening of the pressure control valve in dependence on the monitored pressure relative to the prescribed pressure as a target.
Such a low-pressure apparatus may be, for example, a chemical vapor deposition (CVD) apparatus, a sputtering apparatus or an evaporation apparatus, which are generally used for the deposition of a layer of a material on a surface of a body, for example a semiconductor body. The material may be a semiconductive material such as, for example, polycrystalline silicon or germanium, a conductive material such as, for example, tungsten, molybdenum or copper, or a dielectric material such as, for example, silicon oxide, silicon nitride or tantalum oxide. Alternatively, such a low-pressure apparatus may be used for the local or complete removal of a layer of, for example, one of the above-mentioned materials, from a surface of a body, for example a semiconductor body, by means of, for example, plasma etching or reactive ion etching.
In integrated circuit manufacturing technology, so-called multi-stepped processes are becoming increasingly important, as the performance of integrated circuits is more and more determined by the quality of the interfaces they are composed of. For example, blanket tungsten (W) chemical vapor deposition (CVD) used for filling vias and contact holes is advantageously carried out in two deposition steps. In a first deposition step using tungsten hexafluoride (WF6) and silane (SiH4) a thin layer of tungsten is grown on, for example, a titanium/titanium nitride (Ti/TiN) layer, which has been deposited in advance and serves as an adhesion/barrier layer. As the thin layer of tungsten needs to be grown in a controlled manner, the first deposition step is advantageously carried out under a relatively low prescribed pressure, for example a pressure of about 5 mbar. In a second deposition step using tungsten hexafluoride (WF6), the vias or contact holes are finally filled with tungsten. In order to keep the process time needed for filling as short as possible, the second deposition step is advantageously carried out under a relatively high prescribed pressure, for example a pressure of about 400 mbar.
Large differences in prescribed pressures cannot be handled by a conventional pressure control valve such as, for example, a butterfly valve, which cannot be stably controlled in its almost fully-closed position and its almost fully-open position and has a limited region for stable control. A conventional pressure control valve suitable for stably controlling a prescribed pressure of, for example, 5 mbar at a given process gas flow and a given capacity of the exhaust pump, cannot be used for controlling a comparatively high prescribed pressure of, for example, above 100 mbar at a similar process gas flow and a similar pump capacity.
One way to cope with this problem is to enlarge the process gas flow supplied to the reactor chamber in such a way that the conventional pressure control valve can again be operated in its stable control region. However, a larger process gas flow decreases the residence time of the process gas inside the reactor chamber and, hence, lowers the efficiency of the process. As a consequence thereof, a needless waste of process gas takes place. Moreover, process costs become unnecessarily high. Another way to circumvent the above problem is to use separate reactor chambers for the different steps, each one of the separate reactor chambers having a pressure control valve and control means and being connected to either a separate exhaust pump or a common exhaust pump. However, since the number of periods required for purging, stabilizing, heating-up and cooling-down increases, the overall throughput decreases, which is not desired. In addition, exposure to a less clean environment in between the steps may, for example, adversely influence the quality of the interfaces of semiconductor devices. Moreover, the use of one reactor chamber connected to an exhaust pump through two separate exhaust pipes, each one of the separate exhaust pipes being provided with a pressure control valve, requires two control means for the one reactor chamber and, hence, a considerable modification of software in existing equipment.
The invention has inter alia for its object to provide a low-pressure apparatus of the kind mentioned in the opening paragraph, which apparatus enables steps to be carried out under very different prescribed pressures without the above-mentioned disadvantages.
For this purpose, in accordance with the invention, the pressure control valve comprises a flow channel, a first flow-through element and a second flow-through element, which first flow-through element and second flow-through element are arranged behind each other in the flow channel in the direction of the gas flow and border respectively a first flow-through opening and a second flow-through opening, at least one of the first flow-through element and the second flow-through element being movable substantially transversely to the direction of the gas flow in order to establish a desired overlap between the first flow-through opening and the second flow-through opening and create a common opening referred to as the valve opening, the first flow-through opening at least being provided with a first opening portion bordered by two first edges, which mutually taper into a pointed end, whereby the movable flow-through element at least is adjustable in a position in which the valve opening exclusively comprises only the pointed end of the first opening portion.
By virtue of the above-stated measures, the pressure control valve is controllable in its almost fully-closed position, which widens the range of prescribed pressures controllable with this valve towards higher pressures and enables the low-pressure apparatus to carry out steps under very different prescribed pressures without calling one of the earlier-mentioned disadvantages into being.
Advantageous embodiments of the low-pressure apparatus in accordance with the invention are described in the dependent claims.
The invention further relates to a method of manufacturing a device, in particular, but not exclusively, a semiconductor device, in which method a body is subjected to steps in the low-pressure apparatus mentioned in the opening paragraph, one of the steps being performed under a relatively high prescribed pressure and another under a relatively low prescribed pressure, whereby the relatively high prescribed pressure is controlled by adjusting the movable flow-through element in a position in which the valve opening exclusively comprises only the pointed end of the first opening portion of the first flow-through opening.
The invention also relates to a pressure control valve comprising a flow channel, a first flow-through element and a second flow-through element, which first flow-through element and second flow-through element are arranged behind each other in the flow channel in the direction of the gas flow and border respectively a first flow-through opening and a second flow-through opening, at least one of the first flow-through element and the second flow-through element being movable substantially transversely to the direction of the gas flow in order to establish a desired overlap between the first flow-through opening and the second flow-through opening and create a common opening referred to as valve opening hereinafter, the first flow-through opening at least being provided with a first opening portion bordered by two first edges, which mutually taper into a pointed end, whereby the movable flow-through element at least is adjustable in a position in which the valve opening exclusively comprises only the pointed end of the first opening portion. Hence, the pressure control valve is controllable in its almost fully-closed position, which widens the range of prescribed pressures controllable using this valve as compared to ranges controllable using conventional pressure control valves.
Advantageous embodiments of the pressure control valve in accordance with the invention are described in the dependent claims.